Interpretive Summary: Escherichia coli O157:H7 is an important foodborne pathogen. Cattle are considered a reservoir for this bacterium. It is common, to test cattle feces to determine if any individual animal is shedding E. coli O157:H7; however, more information about where in the cattle gastrointestinal tract E. coli O157:H7 can be found is needed to develop interventions. In animals that were fecal shedding E. coli O157:H7, we found E. coli O157:H7 in samples from the mouth, pharynx, tonsils, lymph nodes, esophagus, all four sections of the stomach, and the small and large intestines, though the specific location of E. coli O157:H7 positive cultures varied between animals. In a larger number of animals presented for harvest, we found E. coli O157:H7 at multiple locations throughout the small and large intestines. Although 31% of the animals were culture positive for E. coli O157:H7 somewhere along the intestinal tract, only 26% of those were fecal-culture positive. These data suggest that fecal shedding underestimated E. coli O157:H7 prevalence in the beef cattle gut and identified potential intervention sites.

Technical Abstract:
Shiga-toxigenic Escherichia coli O157 (STEC O157) occurrence was determined along the entire gastrointestinal tract (GIT) of four naturally-infected cattle and at specific locations for 61 additional animals. STECO157 was recovered along the entire length of the GIT, though inter-animal distribution was variable. Fecal shedding underestimated STECO157 prevalence in the gut.